Ovarian hyperstimulation syndrome (OHSS) represents an exaggerated response to controlled ovarian stimulation (COS) that in some cases could be life-threatening. Assuming that complete prevention of OHSS is not possible, several strategies could be carried out to reduce the risk and early identification of risk factors represents the first step of a multi-stage process. Some well-established risk factors that could rise the risk of OHSS include young age, polycystic ovary syndrome, prior hyper-response/OHSS. In recent years research has focus on identifying biomarkers/hormonal markers that could represent potential predictors of OHSS (anti-Mullerian hormone and antral follicle count). The possible prevention strategies available for the clinician could be divided into primary and secondary. Primary prevention includes personalized stimulation protocols in order to suit patients' characteristics (individually tailored COS, use of GnRH antagonist stimulation protocols, in vitro maturation). Secondary prevention includes all strategies directed to counteract an excessive ovarian response (cycle cancellation, coasting, trigger ovulation by low doses of hCG or by alternative agents, cryopreservation of oocytes/embryos, adequate luteal phase support). So far, the combined use of a GnRH antagonist protocol with GnRH agonist triggering and oocyte and embryo freezing could not be recommended as a standard preventive measure, but it surely represents a promising one.

Ovarian hyperstimulation syndrome (OHSS) represents an exaggerated response to controlled ovarian stimulation (COS) that in some cases could be life-threatening. Assuming that complete prevention of OHSS is not possible, several strategies could be carried out to reduce the risk and early identification of risk factors represents the first step of a multi-stage process. Some well-established risk factors that could rise the risk of OHSS include young age, polycystic ovary syndrome, prior hyper-response/OHSS. In recent years research has focus on identifying biomarkers/hormonal markers that could represent potential predictors of OHSS (anti-Mullerian hormone and antral follicle count). The possible prevention strategies available for the clinician could be divided into primary and secondary. Primary prevention includes personalized stimulation protocols in order to suit patients' characteristics (individually tailored COS, use of GnRH antagonist stimulation protocols, in vitro maturation). Secondary prevention includes all strategies directed to counteract an excessive ovarian response (cycle cancellation, coasting, trigger ovulation by low doses of hCG or by alternative agents, cryopreservation of oocytes/embryos, adequate luteal phase support). So far, the combined use of a GnRH antagonist protocol with GnRH agonist triggering and oocyte and embryo freezing could not be recommended as a standard preventive measure, but it surely represents a promising one.